DENVER BUSINESS JOURNAL - A $4 billion deal would combine two leaders in the online discount stock brokerage space.

St. Louis-based Scottrade Financial Services Inc. said Monday it has agreed to be acquired by Omaha-based rival TD Ameritrade Holding Corp. (NYSE: AMTD) in a cash and stock deal. The announcement follows several weeks of reports that TD Ameritrade had made a bid.

Scottrade founder and CEO Rodger Riney, who owns the company with his family, will join TD Ameritrade's board after the deal closes. Riney revealed in November that he is undergoing treatment for multiple myeloma, a form of blood cancer.

Riney's 75 percent share in Scottrade is valued at about $2.2 billion, according to Bloomberg.